Application of supercritical carbon dioxide for the extraction of alkylresorcinols from rye bran

The use of supercritical CO2 (SC-CO2) for extracting alkylresorcinols from rye bran was investigated. For pure SC-CO2, 35 MPa and 55 °C were used. SC-CO2 with 10% ethanol or methanol as co-solvents was tested at four pressure levels (8, 15, 30 and 35 MPa) and two temperatures (40 and 55 °C). Experiments were conducted at a constant SC-CO2 flow of 5 g/min for 2 h. For comparative purposes acetone at ambient temperature and pressure was also used for extraction. The best extractions were achieved when SC-CO2 was used with co-solvents. At 55 °C and 15-30 MPa, the use of SC-CO2 with co-solvents has yielded from 8 to 80% (w/w) more extracted product than acetone. Yield of extracts was proportional to pressure (when above 30 MPa) and temperature. The results suggest that cleaner bran extracts can be obtained by using pure SC-CO2 followed by the addition of co-solvents. There is no clear advantage of using either methanol or ethanol.